Miniaturized encapsulated ultrasonic transducer

ABSTRACT

An endoscope, especially for transesophageal echocardiography. An encapsulated ultrasonic transducer capsule is provided having a self-contained electro-mechanical sector scanner. A sealed housing is formed which includes axially aligned tubular sections, one of magnetic material and the other of acoustically transparent plastic. A tubular shaft is journalled axially within the housing for limited sector scanning rotation. A magnetic rotor is fixed to the shaft for operation within the magnetic housing section and a transducer element is fixed to the shaft within the other tubular section. Conductor wires for activating the transducer are fixed at one end of the capsule and extend axially through the tubular shaft for connection to the transducer. Position sensing means are incorporated within the capsule. The construction enables the capsule to be highly miniaturized and greatly improved relative to known devices of its type.

This application is a continuation of our copending application Ser. No.160,359, filed Feb. 25, 1988, now U.S. Pat. No. 4,834,102, granted May30, 1989.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a new and improved ultrasonic sector scanner.More particularly, the invention is directed to a unique construction ofa miniaturized mechanical section scanner capsule.

In echocardiography, and other diagnostic practices utilizingultrasound, it is common to utilize an ultrasound transducer deviceapplied externally to the body for the transmission and reception and.acoustic pulses. In the so-called B-mode diagnostic procedures, adesignated area of the body is scanned with acoustic pulses, and theechoes from such pulses are displayed in real time on a CRT (cathode raytube 2) display. These procedures are non-invasive and easily performed,and have become used rather widely in a variety of fields, includingcardiology.

One of the limitations of echocardiographic diagnosis, using an externaltransducer element, is the character of the intervening materialsbetween the transducer and the heart (or other organ) being examined.For example; an externally applied acoustic pulse may be attenuated ordistorted by the intervening presence of rib material, air pockets fromthe lungs, etc. This limits the areas from which the heart, for example,may be effectively acoustically scanned from the exterior of the body.In addition, patients having pulmonary disease or obesity problems maynot be capable of useful cardiographic diagnosis by externally appliedultrasound.

Heretofore, it has been proposed to mount ultrasonic scanning devices atthe distal end of an endoscope device, which can be inserted into thebody. For example, for echocardiography, it has been proposed to insertsuch an endoscope into the esophagus. By this means, it is possible tolocate an ultrasonic scanning device at the level of the heart, withinthe esophagus, and transmit acoustic pulses laterally into the heart.Because of the close positioning of the scanning device, and the minimumamount of intervening material to be traversed, a sharp, high qualityecho image can be obtained. Additionally, using an endoscope with acontrollably bendable distal end, it is possible to position thescanning device within the stomach, oriented to direct acoustic pulsesupward into the heart from below. This provides a viewing perspectivewhich is not possible to achieve using external transducer devices.

Although the use of a transesophageal endoscope for echocardiography hasmany obvious advantages over external devices, the actual utilization ofsuch devices has been severely limited by the extremely high cost and/orimpracticability of the devices heretofore provided. In general,ultrasonic sector scanners are of two types: Electronically drivenarrays and mechanical sector scanners. Array devices are well suited formounting on an endoscope, because they can be highly miniaturized andhave no moving parts. The scanning of an arcuate sector is achieved bysequential or phased activation of individual transducer elementsphysically arranged to project at different angles over the includedsector. With a mechanical sector scanner device, a single transducerelement is mounted for controlled, high speed rocking motion, beingpulsed repeatedly during each scanning cycle.

While theoretically ideal for endoscope application, the use of arrayscanners for echocardiography and other end uses has been sharplylimited by the prohibitively high cost of such equipment. Mechanicalsector scanners, on the other hand, while capable of being produced atonly a fraction of the cost of that of a array scanner, have up to nowbeen completely unsuitable for practical clinical use and have beenemployed, if at all, only under laboratory conditions.

Because space requirements are extremely constrained for anendoscope-mounted transducer suitable for passage through the esophagus,for example, the conventional approach to the utilization of mechanicalsector scanners in such applications has involved the use of a drivemotor mounted at the proximal (external) end of the endoscope andarranged to manipulate an echo device at the distal end through remotedrive means. In some cases, an elongated, rotatable drive shaft has beenemployed; in others, a string and pulley drive arrangement has been usedto transmit motion from the remote drive motor to the internal echodevice. In practice, these devices have been of very limited usefulness,because of the inherent error in relating, with the necessary precision,the position of the remote drive motor to the position of the internalecho device. The substantial distance between these two devices allowstoo much stretch and distortion in the intervening drive means.

One attempt to avoid the problems of the remote drive device isrepresented by the Suwaki et al. U.S. Pat. No. 4,375,818. There, among avariety of proposals offered, is an arrangement in which a drive motor,gear box and rockable mechanical sector scanner are mounted at thedistal end of an endoscope, within an oil-filled bag. Such a device isnecessarily large and bulky, and not s able for general clinical use intransesophageal and similar applications. The size of the device is ofobvious importance in that, first, it must easily enter and move throughthe esophageal passage and, secondly, possible discomfort of the patientmust be minimized.

A feature of the present invention is the design and construction of ahighly reliable, highly precise mechanical sector scanner devicesuitable, for example for endoscope mounting, which is entirelyself-contained within an extremely small capsule and thus ideally suitedfor such applications as transesophageal echocardiography. The device ofthe invention, produceable at a fraction of the cost of electronicarrays, and altogether free of the important disadvantages of priormechanical scanner devices, is well suited for general diagnostic use.

Pursuant to the invention, a precision mechanical sector scanner devicemay be contained in a capsule of approximately one cm in diameter andabout three cm in length, ideally suited for attachment to the distalend of an endoscope device.

In accordance with one aspect of the invention, a unique form ofmechanical sector scanner device is provided, in which a magnetic rotaryelement and transducer element are fixed to a common shaft, mountedwithin an oil-filled, sealed, cylindrical capsule for rotation through apredetermined sector scanning angle. The capsule housing comprises twocoaxially aligned tubular housing sections joined end to end. One of thehousing sections is formed of magnetic material and surrounds themagnetic rotor, while the other housing section is formed ofacoustically transparent plastic material and surrounds the transducerelement.

To particular advantage, the common shaft, to which the rotor andtransducer means are fixed, is of tubular construction, and flexibleconductor wires, for activating the transducer, extend through thecenter of the shaft. These conductors are connected at their outer endsto the transducer crystal, and at their inner ends to a fixed terminalplate. During sector scanning operations, the motion of these conductorwires is limited to a slight back and forth twisting motion.

Position sensing means is contained within the sealed capsule andprovides constant feedback of the exact angular orientation of thetransducer crystal. This enables the CRT display to be preciselysynchronized with the position of the transducer. Moreover, it enableshigh precision control over the motions of the crystal during itsscanning operations.

As a specific advantageous feature, one end of the transducer capsule isformed by a terminal plate having axially projecting conductor pinselectrically connected to the various elements within the capsule. Thisenables the capsule to be literally "plugged in" to a socket boardprovided at the distal end of the endoscope device. The device of theinvention utilizes a practical minimum number of individual parts andderives an optimum level of performance therefrom. This enables thedevice to be miniaturized without creating excessive cost in themanufacturing operation or compromising performance.

For a better understanding of the above and other features andadvantages of the invention, reference should be made to the followingdetailed description of preferred embodiments of the invention and tothe accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an endoscope device having a controllablybendable distal end and carrying at its distal end extremity amechanical sector scanning capsule according to the invention.

FIG. 2 is a highly enlarged, longitudinal cross sectional view of thetransducer capsule of the invention, illustrating also the means formounting the same at the end of an endoscope device.

FIG. 3 is an axial end view of one of the shaft bearing members utilizedin the new transducer unit.

FIGS. 4 and 5 are elevational and plan views respectively of a motorcoil used in the device of the invention, shown in flat form asoriginally wound.

FIGS. 6 and 7 are end elevational and perspective views illustrating apair of motor coils shaped into semi-cylindrical configuration for usein the device of FIG. 2.

FIG. 8 is a perspective view of a transducer element utilized in thedevice of FIG. 2.

FIG. 9 is a perspective view, similar to FIG. 8, showing the transducerelement attached to a generally semi-cylindrical body member.

FIG. 10 is a cross sectional view through a section of the capsulehousing, illustrating another of the shaft bearing portions.

FIG. 11 is a cross sectional view as taken generally on line 11--11 ofFIG. 2, illustrating the manner of mounting the transducer device withinthe capsule housing.

FIG. 12 is a fragmentary, longitudinal cross sectional view through oneof the housing sections.

FIG. 13 is a simplified, developed representation of one form ofposition-sensing device utilized for sensing the angular position of thetransducer element.

FIG. 14 is a fragmentary, longitudinal cross sectional view,illustrating a modified form of device for sensing the angular positionof the transducer element.

FIG. 15 is a simplified, schematic representation of another alternativeform of position-sensing device, using optical means.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawing, and initially to FIGS. 1 and 2 thereof,the reference numeral 10 designates in a general way an endoscope devicewhich for the most part, may be of a standard commercial type, such asMACHIDA GT-8-60US. The endoscope device includes a control handle 11,and a guide tube 12 provided with a manipulatable distal end 13. Theendoscope device, which per se forms no part of the invention, is formedat its distal end by a plurality of hingedly connected link members 14and a terminal collar member 15. A pair of control wires (not shown)extend through the guide tube 12 and are connected at their distal endsto the hinged links 14. At the remote end of the device, the controlhandle 11 is provided with a movable manipulating lever 16 which can bepivoted in one direction or the other to deflect the distal end of theendoscope, as indicated in phantom lines in FIG. 1. Typically, a lockinglever 17 is provided to secure the endoscope in an adjusted position.

In the illustrated device, a transducer capsule 18 is secured to the endextremity of the endoscope. Conductor wires, for operating thetransducer capsule and deriving its output are passed through the guidetube 12 and exit the device through an outlet tube 19 and cable 20. Thecable 20 leads to an electronic control station, including operatingcontrols, CRT etc. (not shown), all of which may be entirelyconventional insofar as this invention is concerned.

With reference now to FIG. 2, the transducer capsule 18 comprises twoprimary housing parts 21, 22. The first housing part 21 is of thin wall,tubular construction and is formed of magnetic material, such as softsteel. Representative dimensions of, the magnetic housing part 21 forthe illustrated device are approximately 0.354 inch in outside diameter,wall thickness of approximately 0.020 inch and length of approximately0.425 inch. The second principal housing part 22 is formed of a plasticmaterial substantially transparent to ultrasonic acoustic pulses, anddesirably having an acoustic impedance similar to that of the humanbody. A preferable material for this purpose is TPX a poly(4-methyl-pentene-1) molding resin marketed by Matsui and ICI. Highdensity polyethylene and polypropylene are also acceptable materials.

Typical (i.e. nonlimiting) dimensions for the second housing part 22 are0.406 inch principal outside diameter and principal wall thickness ofabout 0.030 inch. Advantageously, the outer housing part 22 is providedwith a cylindrical wall extension 23 arranged to be telescopicallyreceived around the outer surface 24 of the metallic sleeve 21. In theassembled device, the metallic sleeve seated against an abutment surface25 formed at the inner end of the plastic housing section 22. In thefinished device, the extension 23 is adhesively bonded to the metallichousing section 21, forming a sealed, rigid joint.

The plastic housing part 22 is provided with an integral partition wall26 provided with a central bore 27 forming a forward journal bearing fora shaft 28. The partition wall 26 forms the inner end of a chamber 29housing an ultrasonic transducer device 30. The partition 26 also formsthe outer end of a chamber 31 housing a magnetic rotor 32 and coils 33of a drive motor.

At the inner end of the rotor chamber 31 there is mounted a bearingmember 34, formed of an engineering plastic, such as Delrin. The bearing34 has a blind bore 35, which forms an inboard bearing for the shaft 28.This is connected to a smaller bore 36 for the passage of conductorwires, as will be further described. The bearing member 34 has a flange37, which is seated against a shoulder 38 on the metallic housing part21 for precise positioning of the bearing member.

A sealed inner end closure for the capsule 18 is formed by means of aterminal plate 39, to be further described, which is seated against theinner face of the bearing 34 and is secured mechanically by bending overof sleeve extensions 40 of the metallic housing part 21. A suitablebonding adhesive is applied prior to the crimping of the sleeve portions40, to assure a fluid-tight closure.

In accordance with the invention, the magnetic rotor element 32 is fixedto a shaft 28, as by a suitable adhesive. Desirably, the rotor member 32is formed of a so-called rare earth material of very high magnetizingforce, i.e., at least about 20×10⁶ gauss-oersteds. Desirable for thispurpose are neodymium-iron-boron type alloys. The rotor element 32 hastypical dimensions of about 0.200 diameter, 0.295 length. The magneticmaterial is polarized north and south on opposite diametral sides.

To advantage, the partition wall 26 and bearing member 34 are providedwith inwardly facing axial bearing surfaces 41, 42 arranged insubstantially contacting relation to end surfaces 43 of the rotor member32. Accordingly, in the assembled unit, the rotor 32, shaft 28 andtransducer unit 30 are all fixed axially by means of the axial bearings41, 42.

Energizing coils 33 for the drive motor advantageously are of agenerally rectangular developed configuration, as shown in FIG. 5. Foroptimum efficiency, axially extending portions 45, 46 of the coils areas long as practicable, in relation to the length of the rotor 32 andthus the coils somewhat overhang the ends of the rotor. To simplifymanufacture, the coils 33 may be wound in flat form, as reflected inFIG. 4. After winding, the coils are shaped around a cylindrical form,taking on a saddle-shaped, semi-cylindrical configuration, as reflectedin FIGS. 6 and 7. The overall width of the coils is such that therespective axial coil portions 45--45 and 46--46 are in relativelyclosely spaced relation, in the assembled motor, leaving a smallV-shaped gap 47 (see FIG. 6). In the illustrated structure, thepartition wall 26 and the bearing wall 34 are provided with annularsurfaces 48, 49 which underlie and support the energizing coils 33.

Mounted on the forward extension 50 of the shaft 28 is the transducerdevice 30, certain details of which are illustrated in FIGS. 8, 9 and11, as well as in FIG. 2. The principal transducer element 51 (see FIG.8) comprises a thin, disc-like piezoelectric crystal 52, advantageouslyof circular configuration. The crystal 52 is mounted on a thinattenuating layer 53, which is in turn mounted on a plastic base 54.Conductors 55, 56 are appropriately connected to the crystal wafer 52and, upon appropriate energizing of the conductors, the crystal 52 willemit acoustic pulses in a well known manner. Electrical signals are alsogenerated by the crystal when it is stimulated acoustically. Theplasticbase 54 is provided with a central axial bore 57, which isreceived on the shaft 28 and bonded thereto with a suitable adhesive.

In the illustrated form of the invention, the transducer device 30includes a semi-cylindrical body member 58, which is mounted upon thecrystal base 54. The body member 58 serves two purposes in theillustrated device. One purpose is to make the crystal device somewhatmore hydrodynamic in its shape, to facilitate relatively rapidoscillating motion of the crystal within a body of oil contained in thecapsule housing. As a second function, the body member 58 provides anappropriate outer surface, coaxial with the shaft 28, for the mountingof a shaped foil member 60 (see FIG. 13) arranged to cooperate with asensing coil 61 for locating and controlling the angular position of thetransducer device 30 relative to its housing. In any operative rotaryposition of the transducer device, a different width portion of the foilsensing element 60 will be located opposite the sensing coil 61. Thischanges the electrical characteristics of the coil, and this is fedthrough conductors back to a main control console (not shown but may beof conventional type). By this means, the instantaneous angularorientation of the transducer device relative to the housing can bedetermined at all times. Additionally, insofar as the momentary angularposition of the device may vary with respect to a desired,pre-programmed orientation, the energizing of the driving motor can bevaried for instantaneous correction. The circuitry for a control of thistype is disclosed in, for example, the Matzuk U.S. Pat. No. 4,092,867.

To particular advantage, the design of the transducer device 30 of thepresent invention, is such as to allow the crystal wafer 52 to belocated as closely as practicable to the center axis of the capsule 18.This enables the diameter of the crystal to be maximized in relation tothe external dimensions of the capsule. Further, in this regard, theinternal wall of the housing part 22 may be milled out slightly to forman annular groove in its lower portions, as reflected at 63, allowingthe diameter of the crystal to be even slightly larger than wouldotherwise be permitted by the sleeve-like housing part 22 (see FIG. 11),for example. Desirably, the milled arcuate groove 63 terminates in theupper portion of the housing part 22, so that the strength of thehousing is maintained, and the sense coil 61 is provided with a smooth,flat area for adhesive securement to the housing.

In normal operation of the device, the transducer device 30 is driven bythe rotor 32 to oscillate through an angle which is both varied andcontrolled electronically at the control station. A stop pin 64 isnevertheless provided, extending from the partition wall 26, tophysically limit the maximum angular displacement of the transducerdevice, shaft and rotor. This is desirable so that the parts do notassume an undesirable orientation during periods of nonuse.

In accordance with one feature of the invention, the shaft 28 is oftubular construction, desirably of a material such as T316 stainlesssteel, 16RW gauge hypodermic tubing. A pair of conductor wires 66, 67extend coaxially through the tubular shaft 28 and are attached at theirouter ends to the crystal conductors 55, 56. At their inner ends, theconductors 66, 67 are connected to the terminal plate 39. To accommodatethis, the back of the bearing member 34 is recessed at 68, to allow theconductors 66, 67 to be redirected after passing through the opening 36.

As will be appreciated, the maximum angular displacement of thetransducer device 30 may be on the order of about 60° to either sidefrom the "neutral" position, as shown in FIG. 11. During normaloperations, the angular displacement typically would be somewhat less.This amount of angular displacement is easily accommodated in afatigue-free manner by a slight twisting of the conductors 66, 67 overtheir relatively substantial longitudinal extent as they pass throughthe center of the tubular shaft 28.

In the device of the invention, external electrical connections areprovided by a plurality of axially disposed terminal pins 70, which arefixed in the terminal plate 39. The terminal plate 39 is constructed inthe form of a printed circuit board having connections for (in theillustrated version of the device) six conductors: The two conductors66, 67 for energizing the transducer and for transmitting its echosignals; two pairs of conductors (not shown) for the motor coils 33, anda pair of conductors 71, 72 leading to the sensing coil 61. The sensingcoil conductors extend through one of the openings 73 in the partitionwall 26, along the V-shaped notch 47 between adjacent motor coils, tosoldered terminals on the terminal plate 39. Printed circuit connections(not shown) connect each of the conductors with a corresponding terminalpin 70, of which six such pins would be provided in the illustrateddevice. The confronting face of the bearing member 34 is provided with aseries of recesses 74 (see FIG. 3) to accommodate the circuit paths andsoldering connections on the terminal plate 39.

In the assembly of the transducer capsule 18, the sleeve-like housingparts 21, 22 are telescopically assembled and secured by adhesive. Thesense coil 61 is installed and secured by adhesive, as are the motorenergizing coils 33. The tubular shaft 28, with the rotor mountedthereon are inserted into the bearing of the partition wall 26, afterwhich the bearing 34 may be put in position and secured by adhesive.After installing the various wires on the terminal board 39, the boardis placed in position, sealed with adhesive and mechanically secured bycrimping of the sleeve end 40. The transducer device can now beinstalled on the shaft and secured by adhesive. A slot 75 in the end ofthe tubular shaft allows the shaft to be held while the transducerdevice is properly oriented relative to the magnetic orientation of therotor 32 and the orientation of the coils 33, so that the transducerdevice is in its middle or neutral position relative to the sensingcoil, as shown in FIG. 11, when the rotor 32 is in its neutral positionrelative to the energizing coils 33. The conductors 66, 67 may then beattached to the transducer conductors 55, 56, following which thecapsule is filled with an appropriate acoustic coupling fluid, such asolive oil or castor oil. All traces of air must, of course, bepositively excluded. After filling with oil, the capsule is sealed byapplying a threaded cap 76, which may also be provided with an O-ring77.

The transducer capsule thus described is entirely self-contained andready for operation. All of the necessary input and output connectionsare available the terminal pins 70.

For mounting of the transducer capsule 18 to the end of the guide tube12, there is provided a transition member 80, in the form of a generallycylindrical sleeve formed of a suitable plastic material, such as TPX.The transition member is provided at its inner end with a neck portion81 which is telescopically received over the terminal collar 15 of theguide tube. The neck portion is applied over the collar until seatedagainst a flange 82, after which it is secured by a pin 83 and typicallyalso by adhesive. To accommodate this assembly procedure, the outersleeve 84 of the guide tube is initially retracted or rolled back toexpose the collar 15. Thereafter, the sleeve is returned to the positionshown in FIG. 2 and secured by adhesive and by tightly wound threads 85.To enhance the securement of the sleeve 84, the neck desirably has asurface 86 tapering convergently toward the outer end of the sleeve 80.This also provides a recess for the reception of the threads 85. Thisrecess is then filled and smoothed with a suitable plastic material 87.

In the illustrated device, the transition member 80 has a steppedinternal surface, including a first portion 88, which is receivedclosely about the outer surface of the metallic sleeve 21, and a secondportion 89, which is closely received over the cylindrical extension 23of the outer housing part 22. Suitable adhesives are utilized to securethese several parts to each other.

Although the transducer capsule 18 is formed in part by the metallicsleeve 21, which forms a flux return path for the motor coils, it isvery undesirable to have any metal exposed on the exterior of thedevice, which could come in contact with the patient. Accordingly, thetransition 80 and outer housing part 22, between them, completelyenclose the metal sleeve 21 with a plastic covering. By providing for anoverlapping arrangement of all three elements, a superior structuralarrangement is provided.

Prior to insertion of the capsule 18 into the transition member 80, theelectrical connections are completed. A first step in this process isthe connection of a socket plate 90 to various conductors extending downthrough the guide tube 12. In the illustrated arrangement, sixconductors may be employed, two of which are reflected at 91 in FIG. 2.These are passed through a central opening 93 in the socket plate anddirected to appropriate terminal points, to which they are soldered. Thesocket plate 90, in this respect, is in the form of a printed circuitboard having desired connection points and conductor paths. In additionto the conductor connection points, the socket plate 90 is provided withopenings for the reception of terminal pins 70 from the transducercapsule. The socket plate may also mount a small tuning inductor 94,which is connected in parallel with the transducer conductors 55, 56.

To establish the electrical connections during manufacture, theconductors extending through the guide tube are pushed axially downwardthrough the guide tube, far enough to project out beyond the transitionmember 80. This allows the various conductors to be properly attachedand soldered to the socket plate 90. Thereafter, the transducer capsulemay be simply "plugged in" to the socket board, and the terminal pins 70advantageously are soldered thereto for good electrical contact. Whenthe transducer capsule is inserted into the transition member 80, theconductors may be simultaneously retracted into the guide tube asneeded.

In the embodiment of the invention shown in FIG. 14, a modified form ofposition-sensing means is provided. In place of the sensing coil 61 andmetal foil 60, of the previously described embodiment, a variableinductor arrangement is provided. The variable inductor device may bemounted at either end of the tubular shaft 128. In the illustration ofFIG. 14, it is mounted at the rearward end closest to the guide tube ofthe endoscope. In the FIG. 14 version, the shaft 128 extends rearwardsomewhat beyond the bearing member 134 and has mounted thereon a plastichub 200 which carries a magnetic element 201 in the form of an arc of acircle concentric about the axis of the shaft 128.

Opposite the shaft 128 is a sleeve 202, secured by a flange 203 to apartition wall 204. The sleeve and flange are of magnetic material andare partially surrounded by an external sleeve 205, also of magneticmaterial. The sleeve 205 is in the form of an incomplete cylinder.Typically, the arc of the magnetic element 201, together with the arc ofthe sleeve 205 total approximately slightly more than 360°.

A sensing coil 206 is wound about the internal sleeve 202, and theinductance of the coil is a variable function of the magnetic pathprovided by the sleeves 202, 205 and the movable magnetic element 201.In the "neutral" position of the shaft 128 (half way between theextremes of rotary displacement in either direction), the movablemagnetic member 201 is symmetrically located relative to the gap in theincomplete sleeve 205. As the shaft is rotated in either direction, themovable magnetic element 201 becomes present to an increasingly greaterextent between the walls of the respective sleeves 202, 205, causingprogressive variation in the inductance of the coil 206, which can beutilized both as a means of locating the rotary position of thetransducer and of correcting its position relative to a programmed cycleof motion.

Other types of position-sensing devices may be utilized in the device ofthe invention, where desired. For example optical devices in themselvesknown in the art, may be attached to or driven by the shaft to providean output of data. A representation of such device is shown in FIG. 15and includes a calibrated transparent encoder disc 301 mounted on ashaft 328. Optical sensing means including light emitting and sensingdevices 303, 304 detect the passage of the code marks for determiningthe exact position of the shaft (and transducer device driven thereby)at all times.

The device of the invention represents a significant advance in thedesign of mechanical sector scanning transducers, in that it enables afull function, rugged, reliable, precision device to be housed within arelatively minute capsule having a diameter of about ten mm and a totallength of less than thirty mm. Within these limited dimensions, thedevice accommodates a transducer having a diameter of approximately 7.5mm, providing for a high degree of power and image resolution inrelation to the minimum size of the transducer capsule. For pediatricapplications, the transducer capsule may be even smaller, for example,six mm diam. The smaller unit typically would be operated at a somewhathigher frequency (e.g, 7.5 MH as compared to 5 MH for an adult unit.)

By providing for a fixed structural relationship between the driverotor, the shaft and the transducer, a high degree of precision ispossible in the positioning of the transducer device and in the sensingof the transducer position, further adding to clarity, precision andresolution of the B-mode display of the scan.

A particularly advantageous feature of the device of the invention isits extremely low part count. Mounting of the rotor 32 and transducerdevice 30 in fixed relation on a common shaft provides for a high degreeof simplification, which also translates into reduced cost and greaterreliability. Further significant advantages in this connection arerealized by the use of a hollow drive shaft and the passing of flexibleconductors through the shaft for connection to the movable transducerdevice. This arrangement results in minimum stress and fatigue on theconductors, and basically occupies no otherwise useable space in thetransducer capsule. Additionally, by locating the conductors on thecenter axis of the shaft, there is absolute minimum hydrodynamicresistance introduced thereby.

The construction of the capsule housing being formed in part by themetal sleeve 21, which surrounds the rotor and forms a return flux path,and in part by the acoustically transparent outer housing 22 furtherminimizes the complexity and part count by allowing an active element ofthe drive motor to form a active part of the capsule housing.

In the device of the invention, the transducer device is designed andmounted so that the active piezoelectric disc is located as close aspracticable to the axis of the main drive shaft, which is as close aspracticable to the maximum diameter of the transducer housing portion(e.g., see FIG. 11). And by forming an annular groove in the housing inthis area, the diameter of the piezoelectric crystal may be even furtherslightly increased for maximum effectiveness.

It should be understood, of course, that the specific forms of theinvention herein illustrated and described are intended to berepresentative only, as certain changes may be made therein withoutdeparting from the clear teachings of the disclosure. Accordingly,reference should be made to the following appended claims in determiningthe full scope of the invention.

We claim:
 1. An ultrasonic sector scanner, which comprises(a) a housingcapsule including an elongated tubular housing section and spaced endwalls forming a sealed enclosure, (b) a tubular shaft mounted axiallywithin said housing and supported therein for limited rotation throughan angle of less than 360°, (c) a rotor magnet fixed to one axialportion of said shaft and rotatable therewith, (d) an ultrasonictransducer unit fixed to a second axial portion of said shaft androtatable therewith, and (e) flexible conductor means extending throughsaid tubular shaft and connected at one end to said transducer unit foractivating the same, (f) one of said housing end walls having terminalconductors passing therethrough in sealed relation, (g) said flexibleconductor means being connected at their other ends to said terminalconductors.
 2. An ultrasonic sector scanner according to claim 1,further characterized by(a) said transducer unit further including abody member having cylindrically contoured surface portions generallyconcentric with the axis of said shaft, (b) said ultrasonic transducerunit comprising a disc-like transducer crystal element mounted on saidbody member and disposed with its axis generally perpendicular to theaxis of said shaft and being mounted as close as practicable to saidshaft, (c) a shaped foil extending circumferentially about thecylindrically contoured surface portions of said body member, (d) aposition sensing coil mounted on the inside of said housing, inalignment with said foil and operative to provide an electrical signalcorresponding to the angular position of said shaft and body member. 3.An ultrasonic sector scanner according to claim 1, further characterizedby(a) said housing comprising a first tubular section formed of plasticmaterial, substantially transparent to ultrasonic acoustical energy,surrounding said transducer unit, (b) said housing further comprising asecond tubular section formed of magnetic material, surrounding saidrotor magnet and joined coaxially with said first tubular section.
 4. Anultrasonic sector scanner according to claim 3, further characterizedby(a) said first tubular housing section having a transverse wallpositioned between said transducer unit and said magnetic rotor andforming a first bearing for said tubular shaft, (b) a second bearingmember mounted at the end of said second tubular section and having asecond bearing supporting one end of said tubular shaft, (c) said firstand second bearings having end surfaces cooperating with said rotormember to form axial thrust bearings for fixing the axial position ofsaid rotor member, shaft and transducer unit.
 5. An ultrasonic sectorscanner according to claim 4, further characterized by(a) electricalmotor coils of arcuate cross sectional configuration mounted within saidsecond tubular housing section and closely embracing said magneticrotor, (b) said motor coils being controllably energizable for drivingsaid rotor in either direction through a limited sector angle, (c) saidtransverse wall and said second bearing member having annular supportsurfaces thereon of slightly larger diameter than the diameter of saidrotor, for supporting said motor coils in closely spaced relation tosaid rotor.
 6. An ultrasonic sector scanner according to claim 5,further characterized by(a) the end wall of said second tubular sectioncomprising a conductor terminal plate mounted in sealed relation withsaid second tubular housing section, (b) terminal conductor meanspassing through said terminal plate in sealed relation, (c) saidterminal conductor means being connected to conductors internally andexternally of said sealed housing for driving and controlling the sectorscanner and deriving its output.
 7. An ultrasonic sector scanneraccording to claim 6, further characterized by(a) said terminal platemounting a plurality of terminal pins projecting axially outward fromsaid plate, (b) circuit means providing conductive connection fromselected terminal pins to selected conductors within said housing, and(c) a socket plate, separate from said sector scanner unit, adapted forconductive reception of said terminal pins for connection of saidscanner unit with external means.
 8. An ultrasonic transducer capsule,which comprises(a) an elongated, sealed tubular housing adapted forcoaxial mounting at the end of an endoscope guide tube, (b) a firstaxial portion of said housing including a sleeve of magnetic material,(c) a second axial portion of said housing being formed of acousticallytransparent material, (d) a shaft mounted coaxially within said sealedhousing for rotation through a limited sector scanning arc, (e) a motorelement fixed to said shaft for rotation therewith within said firstaxial housing portion, (f) electrically energizable coil means withinsaid first axial housing portion for bidirectional rotation of saidmotor element, (g) an ultrasonic transducer element fixed to said shaftportion, (h) stop means within said sealed housing for limiting rotationof said shaft, motor element and transducer to an angle of less than360°.
 9. A capsule according to claim 8, further characterized by(a)said sealed housing being formed in part by the sleeve of magneticmaterial.
 10. An ultrasonic transducer capsule according to claim 8,further characterized by(a) said shaft being of tubular construction,(b) conductor wires extending axially through said tubular shaft, (c)said conductor wires being fixed at one end to one end of said sealedhousing and being fixed at the other end to said transducer element andmovable therewith during sector scanning oscillations of said transducerelement.
 11. An ultrasonic transducer capsule according to claim 8,further characterized by(a) first and second shaft bearings positionedwithin said sealed housing and journalling said shaft, (b) said shaftbearings having axial bearing surfaces cooperating with opposite ends ofsaid motor element to axially confine said motor element and therebyposition axially said shaft and transducer.
 12. An ultrasonic transducercapsule according to claim 8, further characterized by(a) positionsensing means for determining the rotary position of said transducerelement within said housing, (b) said position sensing means comprisinga sensing coil carried on an inner wall of said second axial housingportion and a shaped foil carried on said transducer element and movablewith respect to said sensing coil upon rotation of said shaft.
 13. Anultrasonic transducer capsule according to claim 8, furthercharacterized by(a) position sensing means for determining the rotaryposition of said transducer element within said housing, (b) saidposition sensing means comprising a first arcuate member, formed ofmagnetic material and mounted in said housing in fixed relation thereto,(c) said position sensing means further comprising a second arcuatemember, formed of magnetic material and mounted on said shaft forrotation therewith.
 14. An ultrasonic transducer capsule according toclaim 8, further characterized by(a) position sensing means fordetermining the rotary position of said transducer element within saidhousing, (b) said position sensing means comprising optical sensingmeans.
 15. An ultrasonic transducer capsule according to claim 14,further characterized by(a) said optical sensing means comprising lightemitting and sensing elements, and a member mounted on said shaft andpositioned between said light emitting and sensing elements foraffecting the passage of light as a function of the position of saidshaft.
 16. In an ultrasonic apparatus, an improved sector scannercomprising(a) an elongated tubular housing, (b) a partition in saidhousing forming a shaft bearing, (c) a tubular shaft journalled in saidbearing and extending axially within said housing, (d) a rotor magnetfixed to one portion of said shaft on one axial side of said bearing,(e) an ultrasonic transducer fixed to said shaft on the other axial sideof said bearing, (f) end wall forming means at opposite ends of saidtubular housing forming therewith a sealed enclosure for the containmentof liquid, (g) at least a portion of said housing surrounding said rotormagnet being formed of magnetic material, (h) at least a portion of saidhousing surrounding said transducer being formed of materialsubstantially transparent to ultrasonic energy, (i) one of said endwalls having electrical terminal conductors passing therethrough insealed relation, (j) transducer activating electrical conductor meansconnected to said transducer, extending axially through said tubularshaft and connected to certain of said terminal conductors, (k) rotordriving coils mounted within said magnetic material housing portion, (l)coil energizing conductors connected respectively to said coils and tocertain ones of said terminal conductors, (m) position sensing meanswithin said sealed enclosure for determining the angular position ofsaid transducer, and (n) control means for controllably oscillating saidrotor, shaft and transducer through a limited sector scanning angle.